Use isbindingresolved when checking imported packages

[ararslan]

Fixes #21578

Marking as WIP until I can figure out how best to test this. Suggestions welcome.

Edit: Tested. 😎

[ararslan]

If ever I can figure out how to test this, should the change be backported to 0.6?

[helgee]

Just for my understanding: What is the rationale for this change? And related, what is wrong with the original test?

Edit: Reading helps 😝

[vchuravy]

This is a notoriously difficult to test edge case since you need a binding in Base that is latent. The change per se is correct. But I haven't thought up a way of properly testing it besides doing Pkg.add("Iterators")....

[tkelman]

we can do Pkg.add("Iterators") during the pkg test and test for other things, if that's the easiest way

[ararslan]

The problem is that just adding Iterators doesn't trigger it—Iterators has to be updated for it to happen.

[tkelman]

there is a part of the pkg test that does an update between 2 known points in metadata history, was there an Iterators update between them?

[ararslan]

Got it tested! 🎉

[tkelman]

and that would fail without the change to base?

[ararslan]

Yep, tried it with and without.

[vtjnash]

This appears to have broken the coverage buildbot (http://buildbot.e.ip.saba.us:8010/builders/coverage_ubuntu14.04-x64/builds/357/steps/Run%20inlined%20tests/logs/stdio)